1. Field of the Invention
The present invention relates to a liquid processing apparatus and a liquid processing method for applying a liquid processing such as a cleaning processing to various substrates such as a semiconductor wafer and an LCD substrate.
2. Description of the Related Art
In, for example, the manufacturing process of a semiconductor device, used is a wafer cleaning apparatus for cleaning a semiconductor wafer with a chemical liquid or a pure water so as to remove the particles, organic contaminants, and metal impurities attached to the wafer and to remove, for example, polymers after the etching processing.
As a wafer cleaning apparatus, known is a so-called “single wafer type cleaning apparatus”, in which a chemical liquid is supplied onto the front and back surfaces of a wafer, which is held on a spin chuck in substantially a horizontal posture, under the state that the wafer is left stationary or is rotated so as to carry out a processing with the chemical liquid, followed by supplying a pure water onto the wafer while rotating the wafer at a prescribed rotating speed and subsequently discharging a drying gas such as a nitrogen gas (N2) onto the wafer while rotating the wafer.
A discharging nozzle is used for a cleaning processing in the single wafer type cleaning apparatus. The discharging nozzle includes, for example, a circular plate and a nozzle hole formed to extend through the circular plate. The circular plate is arranged to face, for example, the back surface of the wafer, and a chemical liquid, a pure water and a drying gas are successively supplied from the nozzle hole into the gap between the wafer and the circular plate thereby cleaning the back surface of the wafer.
It should be noted that an unused chemical liquid is left inside the nozzle hole after the discharging of the chemical liquid from the nozzle hole of the discharging nozzle. The chemical liquid left within the nozzle hole is extruded into the gap between the wafer and the circular plate when a pure water is discharged in the subsequent step from the nozzle hole. The unused chemical liquid thus extruded from the nozzle hole is mixed with the used chemical liquid and the pure water so as to drop from the circular plate, or to be centrifugally removed from the wafer when the wafer is rotated. Then, the chemical liquid is recovered. It should be noted that the chemical liquid thus recovered is diluted with the pure water. In addition, a large amount of particles are contained in the recovered chemical liquid. It follows that great expenses are needed for the purifying treatment required for the reuse of the recovered chemical liquid.
It should also be noted that a pure water remains inside the nozzle hole of the discharging nozzle after discharging of the pure water from the nozzle hole to the wafer. If a nitrogen gas is spurted from the nozzle hole under this state, most of the pure water remaining inside the nozzle hole is extruded by the drying gas when the spurting of the drying gas is started. However, since the nozzle hole is arranged to extend in the vertical direction, the pure water remaining inside the nozzle hole is affected by the gravity and, thus, is unlikely to be discharged completely. It follows that the pure water is partly attached to wall of the nozzle hole. If the drying gas is spurted from the nozzle hole under the state that the pure water is partly attached to the wall of the nozzle hole, the pure water is converted into a mist by the vigorous stream of the drying gas. Naturally, the mist is spurted toward the water together with the drying gas. If the mist is attached to that portion of the wafer which has already been dried, a water mark is generated so as to degrade the wafer.